#define _REENTRANT
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<pthread.h>
#include<semaphore.h>

void* thread_function(void* arg);
pthread_mutex_t work_mutex;

#define WORK_SIZE 1024
char work_area[WORK_SIZE];
int time_to_exit = 0;

int main(void)
{
	int res;
	pthread_t a_thread;
	void* thread_result;
	
	res = pthread_mutex_init(&work_mutex, NULL);
	if (0 != res)
	{
		perror("Mutex initialization failed");
		exit(EXIT_FAILURE);
	}
	
	res = pthread_create(&a_thread, NULL, thread_function, NULL);
	if (0 != res)
	{
		perror("Thread creation failed");
		exit(EXIT_FAILURE);		
	}

	pthread_mutex_lock(&work_mutex);
	printf("Input some text, Enter 'end' to finish\n");
	while (!time_to_exit)
	{
		fgets(work_area, WORK_SIZE, stdin);
		pthread_mutex_unlock(&work_mutex);

		while (1)
		{
			pthread_mutex_lock(&work_mutex);
			if (work_area[0] != '\0')
			{
				pthread_mutex_unlock(&work_mutex);
				sleep(1);
			}
			else
			{
				break;
			}
		}
	}

	pthread_mutex_unlock(&work_mutex);
	printf("\nWaiting for thread to finish...\n");
	res = pthread_join(a_thread, &thread_result);
	if (0 != res)
	{
		perror("Thread join failed");
		exit(EXIT_FAILURE);
	}

	printf("Thread joined\n");
	pthread_mutex_destroy(&work_mutex);
	
	return 0;
}

void* thread_function(void* arg)
{
	sleep(1);

	pthread_mutex_lock(&work_mutex);
	while (strncmp("end", work_area, 3) != 0)
	{
		printf("You input %ld characters\n", strlen(work_area) - 1);
		work_area[0] = '\0';

		pthread_mutex_unlock(&work_mutex);
		sleep(1);

		pthread_mutex_lock(&work_mutex);
		while (work_area[0] == '\0')
		{
			pthread_mutex_unlock(&work_mutex);
			sleep(1);
			pthread_mutex_lock(&work_mutex);
		}
	}

	time_to_exit = 1;
	work_area[0] = '\0';
	pthread_mutex_unlock(&work_mutex);

	pthread_exit(0);
}
